1. Field of the Invention
The present invention relates to a smart paper tray and, more particularly, to a smart paper tray which enables the determination of the size of paper loaded into the tray.
2. Description of the Related Art
Printing apparatus commonly use a plurality of paper trays to enable printing on different sizes of paper. In order to enhance productivity of the apparatus, it is desired to know exactly the size paper present in the paper tray to enhance the printing operation on the paper. By knowing what size paper is present in the paper tray, throughput of the printing apparatus can be maximized to, for example, reduce the time required for a printing operation. Accordingly, a printing apparatus having the ability to know exactly what size paper is present can enhance the maximum pitches used in the apparatus.
In the past, this has been achieved by using a series of switches and the logic of on/off switch positions to detect the presence of common paper sizes.
U.S. Pat. No. 5,110,106 to Matsumura et al. discloses one such sheet size detector. A plurality of detectors SA1 through SA4 and SB1 through SB3 are arranged at predetermined intervals along respective moving paths of cams. When a sheet contained in a sheet feed tray is biased by sheet guides, the detecting means located at the position where the sheet guides are stopped are operated to transmit sheet size signals representing sheet size range increments. Microswitches are used as the detecting means. Sheet size can only be determined in accordance with the predetermined location of the switches. Accordingly, only sheet size range increments can be determined. The apparatus does not determine specific sheet sizes since the switches are not mounted on slides contacting the paper edges. The reference even acknowledges that the device is not dedicated to accurately detecting a single sheet size, but rather detects a size range increment including a range of individual sheet sizes (see column 6, lines 3-7).
Accordingly, it would be desirable to enable determination of specific paper sizes present in a paper tray by accurately determining the width and the length of the paper. In accordance with such a determination, the logic of the printing apparatus can run the paper in a mode enhancing the maximum pitches to add maximum throughput.